A substrate is disposed on a substrate holder within a process module. The substrate includes a mask material overlying a target material with at least one portion of the target material exposed through an opening in the mask material. A plasma is generated in exposure to the substrate. For a first duration, a bias voltage is applied at the substrate holder at a first bias voltage setting corresponding to a high bias voltage level. For a second duration, after completion of the first duration, a bias voltage is applied at the substrate holder at a second bias voltage setting corresponding to a low bias voltage level. The second bias voltage setting is greater than 0 V. The first and second durations are repeated in an alternating and successive manner for an overall period of time necessary to remove a required amount of the target material exposed on the substrate.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A system for plasma etching of a target material in semiconductor device fabrication, comprising: a coil; a primary radiofrequency (RF) power supply connected to supply RF power to the coil to generate a plasma; a substrate holder configured to support a substrate in exposure to the plasma; a bias RF power supply connected to generate and transmit RF signals to the substrate holder for generating a bias voltage at the substrate holder, the bias RF power supply including a first RF generator, a second RF generator, and impedance matching circuitry, wherein the first RF generator and the second RF generator are configured to operate independently of each other; RF synchronization logic configured to synchronize operation of the primary RF power supply, the first RF generator, and the second RF generator to enable generation of the bias voltage at the substrate holder and supply RF power to the coil as required for each of two alternating process states, wherein the RF synchronization logic is configured to direct operation of the first RF generator and the second RF generator to generate a high bias voltage at the substrate holder using high frequency RF signals in conjunction with directing operation of the primary RF power supply to supply low RF power to the coil during a first state of the two alternating process states, and wherein the RF synchronization logic is configured to direct operation of the first RF generator and the second RF generator to generate a low bias voltage at the substrate holder using low frequency RF signals in conjunction with directing operation of the primary RF power supply to supply high RF power to the coil during a second state of the two alternating process states, wherein the low bias voltage is greater than zero, wherein the RF synchronization logic includes software.
2. The system as recited in claim 1 , wherein the RF synchronization logic is configured to enable communication between the first RF generator and the second RF generator, and wherein the first RF generator is configured to operate as a master RF generator, and wherein the second RF generator is configured to operate as a slave RF generator responsive to signals received from the first RF generator, and wherein the first RF generator is configured to direct the second RF generator when to output RF signals to the substrate holder.
3. The system as recited in claim 1 , wherein the RF synchronization logic is implemented as a combination of hardware and software.
4. The system as recited in claim 1 , wherein the RF synchronization logic is implemented in each of the first RF generator and the second RF generator.
5. The system as recited in claim 1 , wherein the RF synchronization logic is configured to direct the first RF generator to operate in a continuous wave mode to supply RF signals in a continuous manner to the substrate holder.
6. The system as recited in claim 5 , wherein the RF synchronization logic is configured to direct the second RF generator to operate in a pulsed manner.
7. The system as recited in claim 6 , wherein operation of the second RF generator in the pulsed manner includes operation of the second RF generator to supply RF signals to the substrate holder during a high phase of a pulse.
8. The system as recited in claim 7 , wherein the first RF generator and the second RF generator are configured to respectively supply RF signals to the substrate holder in an additive manner during the high phase of the pulse.
9. The system as recited in claim 1 , wherein the coil is configured to generate an electromagnetic field in response to the RF power to generate the plasma.
10. The system as recited in claim 1 , wherein the low bias voltage is low enough to avoid ion-induced removal of a mask material from the substrate.
11. The system as recited in claim 1 , wherein the RF synchronization logic is configured to control a duration of the first process state and a duration of the second process state, the RF synchronization logic configured to direct a change from the first process state to the second process state following completion of the duration of the first process state, the RF synchronization logic configured to direct a change from the second process state to the first process state following completion of the duration of the second process state, the RF synchronization logic configured to continue directing change from the first process state to the second process state and from the second process state to the first process state for an overall period of time.
12. The system as recited in claim 11 , wherein the duration of the first process state is different than the duration of the second process state.
13. The system as recited in claim 11 , wherein the duration of the first process state is substantially equal to the duration of the second process state.
14. The system as recited in claim 11 , wherein the duration of the first process state is less than ten percent of a sum of the duration of the first process state and the duration of the second process state.
15. The system as recited in claim 11 , wherein the RF synchronization logic is configured to direct the primary RF power supply to supply the low RF power to the coil within a range extending from about 50 Watts (W) to about 2000 W.
16. The system as recited in claim 11 , wherein the RF synchronization logic is configured to direct the primary RF power supply to supply the high RF power to the coil within a range extending from about 2000 W to about 5000 W.
17. The system as recited in claim 11 , wherein the RF synchronization logic is configured to direct the primary RF power supply to supply RF signals of higher frequency to the coil during the first process state, and wherein the RF synchronization logic is configured to direct the primary RF power supply to supply RF signals of lower frequency to the coil during the second process state.
18. The system as recited in claim 17 , wherein the RF signals of higher frequency have a frequency within a range extending from about 13 megaHertz (MHz) to about 60 MHz, and wherein the RF signals of lower frequency have a frequency within a range extending from about 400 kiloHertz (kHz) to about 2 MHz.
19. The system as recited in claim 1 , wherein the high bias voltage is within a range extending from about 400 Volts to about 3000 Volts.
20. The system as recited in claim 1 , wherein the high frequency RF signals have a frequency within a range extending from about 13 megaHertz to about 60 megaHertz.
21. The system as recited in claim 1 , wherein the low bias voltage is within a range extending from about 20 Volts to about 300 Volts.
22. The system as recited in claim 1 , wherein the low frequency RF signals have a frequency within a range extending from about 400 kiloHertz to about 2 megaHertz.
23. The system as recited in claim 1 , wherein the low bias voltage is less than a voltage required to cause ion induced sputtering of a mask material present on the substrate.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
November 20, 2017
June 29, 2021
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